The present invention relates to optical sensors and, more particularly, to optical sensors and transducers for sensing various physical parameters using diffracted optical energy.
Diffraction gratings are typically formed by ruling parallel notches into the surface of a flat substrate with each notch serving as a source of scattered light. When light is transmitted through a grating, the emerging light includes periodic variations in the emerging wavefront. In contrast, when light is reflected from such a surface, the scattered light will arrive at some destination with a phase relationship that produces an interference pattern that varies in an amplitude and wavelength dependent manner.
Diffraction gratings have been used in various applications to assist in analyzing light energy consequent to an intended function. For example, U.S. Pat. No. 3,818,498 to Tomlinson discloses the use of a diffraction grating having a tapered period in which multi-wavelength light is separated into its constituent components to thus provide optical channel droppers, wavelength-selective beam splitters, reflectors, and filters, these devices of particular utility in the optical communications area. Similarly, U.S. Pat. No. 4,408,884 to Kleinknecht discloses using a diffraction grating to detect patterns that are formed on a silicon wafer as an incident to the quality control function.
Various optical sensing techniques have been developed to use light to measure displacements of a selected member as well as changes in an environmental characteristics, such as temperature or pressure. While diffraction gratings have been used in different applications, as mentioned above, the potential for using diffractions gratings in displacement and environmental sensing applications has not been fully realized.